Gas cooking appliance and gas cooking method

ABSTRACT

According to one implementation a cooking appliance is provided that includes an enclosure, a controller, a gas burner and an electrovalve. The electrovalve is capable of assuming an open position where the passage of gas the gas burner is allowed and a closed position where the passage of gas to the gas burner is not allowed. The incandescent element is suitable for igniting the gas burner when the electrovalve is open and gas is being supplied to the gas burner. According to one mode of operation the controller is adapted to control the position of the electrovalve and the amount of current being delivered to the incandescent element so that only the incandescent element provides heat to the enclosure to maintain the enclosure temperature close to a specific set-point temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application relates to and claims the benefit and priority to Spanish Patent Application No. P201430358, filed Mar. 14, 2014.

TECHNICAL FIELD

The present invention relates to a gas cooking appliance and gas cooking methods.

BACKGROUND

Gas cooking appliances comprising an enclosure, a control unit, a burner, an electrovalve, and at least one incandescent element are known. The electrovalve comprises an open position where the passage of gas to the burner is allowed and a closed position where the passage of gas to the burner is not allowed. The incandescent element is suitable for being able to be heated until reaching the gas combustion temperature and for igniting the burner when the electrovalve is open.

EP1847780 A1 discloses a gas oven comprising an enclosure, a gas burner arranged in the lower part of the enclosure, a first electrovalve feeding the burner in an all or nothing manner, a second electrovalve regulating the passage of gas towards the burner for the purpose of regulating the temperature of the enclosure, an incandescent element and an ionization electrode. The incandescent element is adapted to ignite the gas burner when both electrovalves are in an open position. The ionization electrode is suitable for detecting the presence of flame in the burner; it is therefore an element that is used to assure oven safety.

SUMMARY OF THE DISCLOSURE

A method suitable for being implemented in a gas cooking appliance comprising an enclosure, a control unit, a gas heating element comprising a gas burner and an electrovalve comprising an open position where the passage of gas to the burner is allowed and a closed position where the passage of gas to the burner is not allowed, and at least one incandescent element. The incandescent element is suitable for being able to be heated until reaching the gas combustion temperature of the gas being supplied to the burner; therefore when the electrovalve is open to provide a flow of gas to the burner the incandescent element is situated to ignite the burner upon reaching the gas combustion temperature.

According to one cooking method the temperature in the oven enclosure is maintained about a specific set-point temperature only by the use of the incandescent element with the control unit controlling the flow of current to the incandescent element. As a result of using only the incandescent element to maintain the temperature of the enclosure about a desired set-point temperature, the temperature fluctuation about the set-point temperature is minimized to create a more homogenous temperature environment than is otherwise achievable by using the gas burner to maintain the temperature of the enclosure about the desired set-point temperature. This is because the heating provided by the gas burner is much greater than the heating supplied by the incandescent element. Therefore, for set-point temperatures below a threshold temperature the temperature of the enclosure ranges or fluctuates less around the set-point temperature when the power is only supplied by the incandescent element. This produces a temperature environment within the enclosure that is stable and more homogenous, an environment optimal for fermenting food products within the enclosure of the cooking appliance. The method is also optimal for other processes, such as, for example, baking bread, pizza or even for making yoghurt.

These and other advantages and features will become evident in view of the drawings and the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a perspective view of a gas cooking appliance according to one implementation.

FIG. 1B shows a schematic depiction of the cooking appliance of FIG. 1A.

FIG. 2 shows a graph of the temperature behavior of the enclosure of the cooking appliance of FIG. 1A according to one heating method.

FIG. 3 shows a circuit diagram of the incandescent element of FIG. 1B connected to a power supply.

FIG. 4 shows a graph of the behavior of an NTC-type incandescent element.

FIG. 5 shows a graph of the behavior of a PTC-type incandescent element.

DETAILED DESCRIPTION

FIG. 1A shows a perspective view of a cooking appliance 1 according to one implementation. FIG. 1B shows a schematic depiction of the cooking appliance 1. The cooking appliance 1 comprises an enclosure 2, a control unit 6, a gas heating element, and at least one incandescent element 3. The gas heating element comprises a gas burner 4. An electrovalve 5 controls the flow of gas to the gas burner 4 by transitioning between an open position where the passage of gas to the burner 4 is allowed and a closed position where the passage of gas to the burner 4 is not allowed. The incandescent element 3 is suitable for being able to be heated until reaching the gas combustion temperature of the gas supplied to the gas burner 4. Therefore, when the electrovalve 5 is in an open position the incandescent element 3 ignites the burner 4 upon the incandescent element 3 reaching the gas combustion temperature of the gas being supplied to the gas burner 4. In some instances the control unit 6 activates or keeps only the incandescent element 3 active to heat and/or to keep the enclosure 2 close to a specific set-point temperature Ts. As previously discussed, according to one heating method the temperature in the oven enclosure is maintained about a specific set-point temperature only by the use of the incandescent element with the control unit controlling the flow of current to the incandescent element.

According to one heating method at least two modes of operation are implemented wherein a first mode is carried out in a temperature range where the selected set-point temperature Ts is greater than or equal to a threshold temperature Tt, and a second mode is carried out in a range where the selected set-point temperature Ts is less than the threshold temperature Tt. The cooking step of the method is carried out in the second mode of operation.

The set-point temperature Ts is the temperature selected by the user of the cooking appliance 1 through a user interface 9 that interacts with the control unit 6 to define the mode of cooking, and the threshold temperature Tt is that temperature at which the burner, due to having excessive power, is not capable of keeping the temperature of the enclosure 2 stable and homogenous within a temperature range or interval that can range between +2.5° C. and −2.5° C. with respect to the set-point temperature Ts. In a non-limiting example, the threshold temperature Tt corresponds to about 65° C., but this temperature may vary depending on the heating capacity of the burner 4. According to some implementations the threshold temperature can range between about 50° C. and about 75° C.

The temperature of the enclosure 2 is kept more stable and more homogenous close to the set-point temperature Ts when the set-point temperature Ts is less than the threshold temperature Tt, According to one implementation the temperature of the enclosure 2 is kept within a temperature interval ΔT between +2.5+ C. and −2.5+ C. with respect to the set-point temperature Ts. In non-limiting examples the temperature interval ΔT ranges between +0.5+ C. and −0.5+ C., or any interval between +0.5+ C. and −0.5+ C. and +2.5+ C. and −2.5+ C., respectively. The power supplied by the burner 4, which can be, for example, in the order of 7 KW is much greater than the power supplied by the incandescent element 3, which can be in the order of 160 W, for example. Therefore, by using the burner 4 as the main heating element, it is not capable of keeping the temperature of the enclosure 2 within the desired temperature interval ΔT due to the inertia of the burner 4 itself when the set-point temperature Ts is less than the threshold temperature Tt. According to some implementations the ratio of the heating capacity (Watts) of the gas burner 4 and the incandescent element 3 is between about 15 to 150.

The second mode of operation produces a temperature environment within the enclosure that is stable and more homogenous, an environment optimal for fermenting a variety products within the enclosure of the cooking appliance. The method is also optimal for other processes, such as, for example, baking bread, pizza or even for making yoghurt. The making of yogurt is a delicate operation that may be, for example, carried out between 20+ C. and 60+ C., and requires special control over the temperature of the enclosure 2. To produce a quality yogurt product and to prevent the creation of unpleasant odors the temperature of the enclosure 2 should be stable and substantially homogenous.

In the second mode of operation the incandescent element 3 alone is used to maintain the temperature within the enclosure 2 about the set-point temperature Ts. According to one implementation this is achieved by the use of the control unit 6 that directly or indirectly controls the flow of current to the incandescent element 3. In the second mode the control unit also acts to cause the electrovalve 5 to close or remain closed to prevent the passage of gas to the burner 4. The incandescent element 3 having sufficient power/heating capacity to maintain the temperature of the enclosure within a desired temperature interval ΔT about the set-point temperature Ts.

According to another implementation, the second mode of operation can comprise a heating step S_(h) wherein the burner 4 and the incandescent element 3 are activated by the control unit 6 for heating the enclosure 2 until reaching the set-point temperature Ts in a first phase, as shown in FIG. 2, and a maintenance step S_(m) wherein only the incandescent element 3 is activated to keep the temperature of the enclosure 2 close to the set-point temperature Ts in a second phase, in the maintenance step the gas burner 4 going into the inactive state. In other words, in this maintenance step S_(m) the control unit 6 keeps only the incandescent element 3 activated in order to keep the temperature of the enclosure 2 within the temperature interval ΔT. This variant is particularly advantageous because the power of the burner 4 is used for rapidly heating the enclosure 2 (to the desired set-point temperature) and then the temperature is maintained only with the incandescent element 3, which contributes to improved energy efficiency and reduced energy cost of the cooking appliance 1 while stability and homogeneity of the temperature of the enclosure 2 are assured. The heating step S_(h) could be dispensed if it is based on a situation where the cooking appliance 1 is already hot.

FIG. 2 shows a graph of an example of the temperature behavior of the enclosure 2 of the cooking appliance 1 which is operating according to the variant of the second mode of operation which comprises the heating step S_(h) and the maintenance step S_(m). The graph reflects temperature “T” on the vertical axis and time “t” on the horizontal axis.

According to one implementation the incandescent element 3 comprises an electric heating element that heats and/or keeps the enclosure 2 hot through convection.

In the first mode of operation the burner 4, being the main heating element, is capable of keeping the temperature of the enclosure 2 within the desired temperature interval ΔT when the set-point temperature Ts is greater than or equal to the threshold temperature Tt. In this first mode of operation, the working temperature range may be, for example, established between 65+ C. and 250+ C. Within this working temperature range, the inertia of the burner 4 does not hinder reaching the set-point temperature Ts and keeping it within the temperature interval ΔT.

Like in the variant of the second mode of operation, this first mode of operation also comprises a heating step wherein the burner 4 and the incandescent element 3 are activated for heating the enclosure 2 until reaching the set-point temperature Ts (the incandescent element 3 contributes to a lesser extent), and a maintenance step wherein both the burner 4 and the incandescent element 3 are kept active to keep the temperature of the enclosure 2 close to the set-point temperature Ts (the incandescent element 3 contributes to a lesser extent).

To control the temperature of the enclosure 2 according to any of the embodiments disclosed or contemplated herein, the cooking appliance 1 comprises a temperature sensor 8, arranged preferably in a top part of the enclosure 2, associated with the control unit 6 so that the control unit 6 correctly manages both the burner 4 and the incandescent element 3.

As depicted in FIG. 3, the incandescent element 3 may be constantly connected to a power supply 7 while the cooking appliance is operating and is suitable for turning on the burner 4 when the electrovalve 5 is open. Optionally, the incandescent element 3 can also be powered directly through a mains socket or indirectly through the control unit 6. Therefore, an unwanted situation of the burner 4 not turning on or turning off can only occur when the incandescent element 3 functions in a faulty manner.

In this sense, the control unit 6 reads and in some instances records the current “I” going through the incandescent element 3. The control unit may comprise a monitoring unit adapted to act on the electrovalve 5 to close it in the event the current “I” read by the control unit 6 indicates an anomaly in the incandescent element 3.

According to one implementation, in the first mode of operation of the cooking appliance 1, the control unit 6, through the monitoring unit, monitors the current “I” of the incandescent element and keeps the electrovalve 5 open if the current “I” that is read is stable and is greater than a pre-established minimum current I_(min), otherwise the control unit 6 will act to close the electrovalve 5.

That described in the preceding paragraph is also applicable to the heating step S_(h) of the second mode of operation of the cooking appliance 1 according to any of the embodiments disclosed or contemplated herein. In other words, the control unit 6 will monitor, through the monitoring unit, the operation of the cooking appliance 1, acting in the event of any anomaly detected in the incandescent element 3 as long as the electrovalve 5 or the burner 4 are enabled for use during normal operation of the cooking appliance 1. Therefore, if an anomaly is detected, the control unit 6 will act to close the electrovalve 5 to prevent the leakage of unburned gas, and the control unit 6 will otherwise keep the electrovalve 5 open.

According to one implementation the current “I” is considered stable when the variation between two consecutive current values read by the control unit is less than 5%. The minimum current I_(min) is defined as the necessary minimum current that must go through the incandescent element 3 so that it is capable of igniting the gas. In the examples of FIGS. 4 and 5, the stable zone corresponds with the zone of the graph line close to the I_(min) line.

According to some implementations the gas burner 4 and the incandescent element 3 of the cooking appliance 1 are arranged in the lower part of the enclosure 2. In a non-limiting example, the incandescent element 3 is arranged at an end of the burner 4, preferably close to the first flame opening of the burner 4. Optionally, the cooking appliance 1 may comprise a second burner 4′ as shown in FIG. 1, in the upper part of the enclosure 2 in the form of a grill. In lieu of a gas burner, the grill element may comprise an electrical radiant heating element.

The incandescent element 3 of the cooking appliance 1 may comprise an NTC-type or a PTC-type behavior. In NTC behavior, the resistance of the incandescent element 3 decreases as its temperature increases, thus increasing the current “I” going through the incandescent element 3. In contrast, in PTC behavior, the resistance of the incandescent element 3 increases as its temperature increases, thus reducing the current “I” going through the incandescent element 3. 

What is claimed is:
 1. A gas cooking appliance comprising: an enclosure, a gas burner located inside the enclosure, a user interface for selecting a desired specific set-point temperature inside the enclosure, an electrovalve located in a gas supply passage of the gas burner, the electrovalve capable of assuming an open position where the passage of gas to the gas burner is allowed and a closed position where the passage of gas to the gas burner is not allowed, at least one incandescent element located in the enclosure adjacent the gas burner, the incandescent element capable of being heated to a gas combustion temperature of a gas supplied to the gas burner and to ignite the gas burner upon reaching the gas combustion temperature, the incandescent element further being capable of providing heat to the enclosure to maintain the enclosure temperature close to the specific set-point temperature; and a controller operatively coupled to the user interface, electrovalve and incandescent element, the controller adapted to cause the electrovalve to assume the open position or the closed position, the controller adapted to control the flow of current to the incandescent element, according to one mode of operation the controller is adapted to cause the electrovalve to transition from the open position to the closed position and to cause the flow of current to the incandescent element to be regulated to maintain the enclosure temperature close to the specific set-point temperature.
 2. A gas cooking appliance according to claim 1, wherein the controller is adapted to cause the electrovalve to transition from the open position to the closed position and to cause the flow of current to the incandescent element to be regulated to maintain the enclosure temperature close to the specific set-point temperature only when the specific set-point temperature is less than a threshold temperature.
 3. A gas cooking appliance according to claim 2, wherein the threshold temperature is between 50+ C. and 75+ C.
 4. A gas cooking appliance according to claim 3, wherein the controller is adapted to control the flow of current to the incandescent element to maintain the enclosure temperature within ±0.5° C. to the specific set-point temperature.
 5. A gas cooking appliance according to claim 1, wherein according to another mode of operation the controller is adapted to cause the electrovalve to assume the open position and to cause the flow of current to the incandescent element to be regulated to ignite the gas burner.
 6. A gas cooking appliance according to claim 5, wherein the controller is adapted to cause the electrovalve to transition from the open position to the closed position upon the enclosure temperature being close to the specific set-point temperature while continuing to regulate the flow of current to the incandescent element.
 7. A gas cooking appliance according to claim 6, wherein according to another mode of operation when the specific set-point temperature is greater than a threshold temperature the controller is adapted to control the position of the electrovalve to cause the gas burner to provide heat to the enclosure to maintain the enclosure temperature close to the specific set-point temperature.
 8. A gas cooking appliance according to claim 7, wherein the controller is adapted to concurrently regulate the flow of current to the incandescent element to assist the gas burner in maintaining the enclosure temperature close to the specific set-point temperature.
 9. A gas cooking appliance according to claim 1, wherein the controller is adapted to control the flow of current to the incandescent element to maintain the enclosure temperature within ±2.5° C. to the specific set-point temperature.
 10. A gas cooking appliance according to claim 1, wherein the ratio of the heating capacity of the gas burner and the incandescent element is between 15 and
 150. 11. A gas cooking appliance according to claim 1, wherein upon an initial heating of the enclosure the controller is adapted to implement a heating step to cause the gas burner and the incandescent element to be activated for heating the enclosure until reaching the set-point temperature and to implement a maintenance step wherein only the incandescent element is kept activated to keep the temperature of the enclosure close to the set-point temperature.
 12. A cooking appliance according to claim 1, wherein the controller is further adapted to read the current flow passing through the incandescent element and, when the electrovalve is in the open position, to cause the electrovalve to maintain the open position only when the current flow read by the controller is stable and greater than a pre-established minimum current.
 13. A cooking appliance according to claim 12, wherein the pre-established minimum current flow is a minimum current flow necessary for the incandescent element to be capable of igniting the gas.
 14. A cooking appliance according to claim 12, wherein the controller determines the flow of current to be stable when the variation between two consecutive current values read by the controller is less than 5%.
 15. A cooking appliance according to claim 1, wherein the incandescent element heats by convection.
 16. A cooking appliance according to claim 7, wherein the threshold temperature is in a range of between 50+ C. and 75+ C.
 17. A cooking appliance according to claim 1, wherein the incandescent element exhibits NTC-type or PTC-type behavior.
 18. A cooking appliance according to claim 1, wherein the gas burner and the incandescent element are arranged in a lower part of the enclosure.
 19. A cooking appliance according to claim 1, wherein the incandescent element is arranged at an end of the gas burner close to a first flame port of the gas burner.
 20. A cooking appliance according to claim 1, wherein the enclosure is an oven cavity. 